A 8 kg box with initial speed 8 m/s slides across a floor and comes to a stop after 1.8 seconds. What is the coefficient of kinetic friction? How far does the box move? You put a 3 kg block in the box, so the total mass is now 11kg, and you launch this heavier box with an initial speed of 8 m/s. How long does it take to stop? What formulas do I need to use and what steps do I take when approaching a question like this?